1. Technical Field
This disclosure relates to a cleaning blade, and to an image forming apparatus and a process cartridge, which use the cleaning blade. In addition, this disclosure relates to a method for preparing the cleaning blade.
2. Description of the Related Art
In electrophotographic image forming apparatuses, residual toner remaining on the surface of an image bearer such as photoreceptors even after a toner image thereon is transferred onto a recording medium or an intermediate transfer medium is removed therefrom using a cleaner.
A strip-shaped cleaning blade made of an elastic material such as polyurethane rubbers is typically used as a cleaning member of such a cleaner because of having advantages such that the cleaner has simple structure and good cleanability. The cleaning blade typically has a configuration such that one end thereof is supported by a supporter, and an edge of the other end is contacted with a surface of an image bearer to block and scrape off residual toner on the surface of the image bearer, thereby removing the residual toner from the surface of the image bearer.
In attempting to fulfill a recent need for high quality images, there are image forming apparatuses using substantially spherical toner (hereinafter sometimes referred to as polymerization toner), which has a relatively small particle diameter and which is prepared by a method such as polymerization methods. Since polymerization toner has such an advantage as to have a higher transfer efficiency than pulverization toner, which has been conventionally used, the polymerization toner can fulfill the need. However, polymerization toner has such a drawback as not to be easily removed from an image bearer by a cleaning blade, resulting in occurrence of a cleaning problem. This is because such polymerization toner has a high circularity and a small particle diameter, and therefore easily passes through a small gap between the tip of a cleaning blade and the surface of an image bearer.
In attempting to prevent occurrence of such a cleaning problem (i.e., toner passing problem), a technique such that the pressure to a cleaning blade contacted with the surface of an image bearer is increased is often used to enhance the cleanability of the cleaning blade. However, it is well known that when the contact pressure of such a cleaning blade is increased, the following problem is caused.
Specifically, as illustrated in FIG. 8A, when the contact pressure of a cleaning blade 62 is increased, the friction between the cleaning blade 62 and an image bearer 123 is increased, and a tip edge 62c of a tip surface 62a of the cleaning blade 62 is pulled by the moving surface of the image bearer 123 in the moving direction of the image bearer 123, thereby everting the tip edge portion of the tip surface 62a of the cleaning blade 62. In this regard, since the thus everted tip edge portion of the cleaning blade 62 has a restoring force, the tip edge portion tends to vibrate, resulting in generation of fluttering sounds (hereinafter referred to as a fluttering sound problem). In addition, when the cleaning operation is continued while the tip edge portion of the cleaning blade 62 is everted, a portion of the tip surface 62a of the cleaning blade 62, which portion is few micrometers away from the tip edge 62c, is abraded as illustrated in FIG. 8B. When the cleaning blade 62 is further used for the cleaning operation, the portion of the tip surface 62a of the cleaning blade 62 is further abraded, resulting in lack of the tip edge 62c of the cleaning blade 62 as illustrated in FIG. 8C. The cleaning blade 62 having no tip edge hardly removes residual toner from the surface of the image bearer 123, thereby causing a cleaning problem in that an abnormal image in which background thereof is soiled with residual toner is formed.
In FIGS. 8A-8C, numeral 62b denotes a lower surface of the cleaning blade 62, which faces the surface of the image bearer 123 to be cleaned.
A cleaning blade is proposed which includes an elastic blade and an outermost layer covering the tip edge portion of the elastic blade, wherein at least the tip edge portion of the elastic blade is impregnated with an ultraviolet crosslinked resin, and the outermost layer is formed of an ultraviolet crosslinked resin. In this regard, a mixture of a fluorine-containing acrylic monomer, an acrylate material including as a main skeleton a pentaerythritol triacrylate while having a functional group equivalent molecular weight (i.e., molecular weight of a compound per one functional group of the compound) of not greater than 350 and 3 to 6 functional groups, and another acrylate material having a functional group equivalent molecular weight of from 100 to 1,000 and 1 to 2 functional groups is used for the ultraviolet crosslinked resin.
It is described in the proposal that by impregnating the elastic blade with the above-mentioned ultraviolet crosslinking resin, the hardness of the tip edge portion of the elastic blade can be enhanced, and thereby deformation (eversion) of the tip edge portion in the moving direction of the image bearer can be prevented. In addition, it is described therein that even when the outermost layer is abraded after long repeated use and the tip edge portion of the elastic blade is revealed, the tip edge portion of the elastic blade, which includes the ultraviolet crosslinked resin, is contacted with the surface of the image bearer, and therefore the friction between the elastic blade and the image bearer is relatively low, resulting in prevention of deformation of the tip edge portion of the elastic blade. Namely, it is described therein that the cleaning blade can prevent deformation (eversion) of the tip edge portion thereof while enhancing the abrasion resistance thereof, thereby making it possible to prevent occurrence of the above-mentioned cleaning problem even when the cleaning blade is used over a long period of time.